冻融损伤喷射混凝土永久支护结构碳化耐久性分析

高纬度、高海拔地区长大公路隧道的喷射混凝土永久支护结构常年遭受冻融损伤及碳化双重作用，其结构耐久性能退化，增大了隧道的养护及运营成本。采用先气冻气融后快速碳化的方式，开展冻融损伤喷射混凝土永久支护结构碳化耐久性试验研究，以冻融损伤喷射混凝土碳化深度和相对抗压强度为指标，研究冻融损伤喷射混凝土碳化深度的变化规律及影响因素。结果表明，冻融损伤加速了喷射混凝土的碳化过程，且碳化速度随冻融损伤度快速增大。碳化的冻融损伤混凝土相对抗压强度随着碳化深度增大。冻融损伤度大于10%时，碳化对冻融损伤喷射混凝土相对抗压强度增长不明显。采用IBM SPSS统计软件对试验数据分析，建立了考虑冻融损伤、喷射混凝土配合比参数及成型方式的喷射混凝土碳化深度预测模型。经验证，预测值与试验值总体误差小于20%，标准误差为0.16，模型适用性较好。

Carbonation durability performance and carbonation prediction model of shotcrete permanent support structure after frost damage

Shotcrete permanent support structure of long highway tunnels in high-latitudes and high-altitudes area is subjected to the action of freeze-thaw damage and carbonation which degraded structure durability performance and increased the tunnel maintenance and operation cost.Carbonation durability of frost-damaged-shotcrete was investigated by using freeze-thaw cycles in air firstly and then accelerated carbonation method.With the evaluating indicator of carbonation depth and relative compressive strength, the deterioration law and influence factor of carbonation depth were researched.Results show that frost damage accelerated the carbonation rate and carbonation depth was deeper with the relative dynamic elasticity modulus decreased.The relative compressive strength of frost damage shotcrete increased with the increasing of carbonation depth.However, when frost damage degree was more than 10%, the influence of relative compressive strength on frost damage shotcrete was not obvious.Furthermore, the carbonation depth prediction model of shotcrete was established considering frost damage degree, shotcrete mixture parameters and concrete forming mode by using IBM SPSS statistical software to analyze the test data.The overall error between the predicted value and the experimental data was less than 20%, and the standard error was 0.16. This indicates that the model has good applicability.